scholarly journals Inhibitory Effect of Cinobufagin on L-Type Ca2+Currents, Contractility, and Ca2+Homeostasis of Isolated Adult Rat Ventricular Myocytes

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Pinya Li ◽  
Qiongtao Song ◽  
Tao Liu ◽  
Zhonglin Wu ◽  
Xi Chu ◽  
...  
Keyword(s):  
Ventricular Myocytes ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Concentration Dependent Manner ◽  
Cell Contractility ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Time To Peak ◽  
Whole Cell Patch Clamp

Cinobufagin (CBG), a major bioactive ingredient of the bufanolide steroid compounds of Chan Su, has been widely used to treat coronary heart disease. At present, the effect of CBG on the L-type Ca2+current (ICa-L) of ventricular myocytes remains undefined. The aim of the present study was to characterize the effect of CBG on intracellular Ca2+([Ca2+]i) handling and cell contractility in rat ventricular myocytes. CBG was investigated by determining its influence onICa-L, Ca2+transient, and contractility in rat ventricular myocytes using the whole-cell patch-clamp technique and video-based edge-detection and dual-excitation fluorescence photomultiplier systems. The dose of CBG (10−8 M) decreased the maximal inhibition of CBG by 47.93%. CBG reducedICa-Lin a concentration-dependent manner with an IC50of 4 × 10−10 M, upshifted the current-voltage curve ofICa-L, and shifted the activation and inactivation curves ofICa-Lleftward. Moreover, CBG diminished the amplitude of the cell shortening and Ca2+transients with a decrease in the time to peak (Tp) and the time to 50% of the baseline (Tr). CBG inhibited L-type Ca2+channels, and reduced[Ca2+]iand contractility in adult rat ventricular myocytes. These findings contribute to the understanding of the cardioprotective efficacy of CBG.

Alpha 1b-adrenoceptor-mediated stimulation of Na-K pump current in adult rat ventricular myocytes

1993 ◽  
Vol 264 (4) ◽  
pp. H1315-H1318 ◽  
Author(s):  
A. P. Williamson ◽  
R. H. Kennedy ◽  
E. Seifen ◽  
J. P. Lindemann ◽  
J. R. Stimers
Keyword(s):  
Adrenergic Receptors ◽  
Ventricular Myocytes ◽  
Pump Current ◽  
Peak Effect ◽  
Patch Clamp Technique ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Whole Cell Patch Clamp ◽  
Dose Dependent ◽  
Stimulation Of

The purpose of this study was to determine if myocardial alpha 1a-and/or alpha 1b-adrenoceptors are involved in the increase in Na-K pump current (Ip) elicited by alpha 1-adrenergic agonists. Single rat ventricular myocytes were isolated by enzymatic disaggregation. The whole cell patch-clamp technique was used to examine dose-dependent effects of phenylephrine (PE) on holding current (Ih) and to determine whether observed actions were mediated via alpha 1a-or alpha 1b-adrenergic receptors. To minimize the contribution of transsar-colemmal currents other than Ip to Ih, membrane voltage was held constant -40 mV, and cells were maintained in a Ca-free perfusate containing 1 mM Ba and 0.1 mM Cd. All experiments were conducted in the presence of 3 microM nadolol. PE elicited dose-dependent increases in Ih, with a peak effect of 0.57 +/- 0.03 pA/pF observed at 30 microM. The response to PE was dose dependently inhibited by prazosin and chloroethylclonidine and was totally eliminated by 1 mM ouabain. When used at doses selective for the alpha 1a-subtype, WB4101 failed to significantly antagonize the action of PE. These data suggest that the observed alpha 1-adrenoceptor-mediated increase in Ih in isolated rat ventricular myocytes is the result of an increase in Ip effected via stimulation of alpha 1b-adrenergic receptors.

Effects of extracellular ATP on ICa, [Ca2+]i, and contraction in isolated ferret ventricular myocytes

1993 ◽  
Vol 264 (3) ◽  
pp. C702-C708 ◽  
Author(s):  
Y. Qu ◽  
H. M. Himmel ◽  
D. L. Campbell ◽  
H. C. Strauss
Keyword(s):  
Action Potential ◽  
Ventricular Myocytes ◽  
Ventricular Myocardium ◽  
Inhibitory Effect ◽  
Extracellular Atp ◽  
Maximal Effect ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Concentration Dependent Manner ◽  
The Right

The effects of extracellular ATP on the voltage-activated "L-type" Ca current (ICa), action potential, resting and transient intracellular Ca2+ levels, and cell contraction were examined in enzymatically isolated myocytes from the right ventricles of ferrets. With the use of the whole cell patch-clamp technique, extracellular ATP (10(-7) to 10(-3) M) inhibited ICa in a time- and concentration-dependent manner. ATP decreased the peak amplitude of ICa without altering the residual current at the end of 500-ms clamp steps. The concentration-response relationship for ATP inhibition of ICa was well described by a conventional Michaelis-Menten relationship with a half-maximal inhibitory concentration of 1 microM and a maximal effect of 50%. Consistent with its inhibitory effect on ICa, ATP hyperpolarized the plateau phase and shortened the action potential duration. In fura-2-loaded myocytes, extracellular ATP did not change the resting myoplasmic Ca2+ levels; however, when current was elicited under voltage-clamp conditions, ATP both decreased the myoplasmic intracellular Ca2+ transient and inhibited the degree of cell shortening. Our results suggest that ATP could be a genuine and potent extracellular modulator of cardiac function in ferret ventricular myocardium.

Effects of Mg2+ on Ca2+ waves and Ca2+ transients of rat ventricular myocytes

1996 ◽  
Vol 270 (3) ◽  
pp. H907-H914 ◽  
Author(s):  
H. Terada ◽  
H. Hayashi ◽  
N. Noda ◽  
H. Satoh ◽  
H. Katoh ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Channel Blocker ◽  
Ventricular Myocytes ◽  
Inhibitory Effect ◽  
Antiarrhythmic Action ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Triggered Activity ◽  
Rat Ventricular Myocytes ◽  
High Concentrations

It has been shown that the occurrence of the transient inward current, which is responsible for triggered activity, was often associated with propagating regions of increased intracellular Ca2+ concentration ([Ca2+]i), i.e., the “Ca2+ wave.” To investigate the mechanism of antiarrhythmic action of Mg2+, we have studied effects of high concentrations of Mg2+ on Ca2+ waves in isolated rat ventricular myocytes. [Ca2+]i was estimated using the Ca(2+)-indicating probe indo 1. Ca2+ waves in myocytes, stimulated at 0.2 Hz, were induced by perfusion of isoproterenol (10(-7) M). High Mg2+ concentration suppressed Ca2+ waves in a concentration-dependent manner (36% at 4 mM, 70% at 8 mM, and 82% at 12 mM). The Ca2+ channel blocker verapamil also suppressed Ca2+ waves in a similar way. In contrast with marked depression of Ca2+ transients by verapamil, Ca2+ transients were not affected by high Mg2+ concentration (8 mM). High Mg2+ concentration also reduced frequencies of Ca2+ waves in the absence of electrical stimulation, whereas verapamil failed to reduce frequencies of Ca2+ waves. Reduction in frequency of Ca2+ waves by high Mg2+ concentration was associated with slowing of propagation velocity of Ca2+ waves. To examine whether suppressive effects of high Mg2+ concentration on Ca2+ waves were related to an increase in intracellular Mg2+ concentration ([Mg2+]i), the effect of high-Mg2+ solution on [Mg2+]i was examined in myocytes loaded with mag-fura 2. An increase in extracellular Mg2+ concentration from 1 to 12 mM increased [Mg2+]i from 1.06 +/- 0.16 to 1.87 +/- 0.22 mM (P < 0.01) in 30 min. To examine the effect of high Mg2+ concentration on amount of releasable Ca2+ in the sarcoplasmic reticulum, the effect of high Mg2+ concentration on the Ca2+ transient induced by a rapid application of caffeine was examined. High-Mg2+ solution increased the peak of the caffeine-induced Ca2+ transient. These results suggest that the inhibitory effect of Mg2+ on Ca2+ waves was not due to inhibition of the sarcolemmal Ca2+ channel but could be due to a decreased propensity for the sarcoplasmic reticulum to divest itself of excess Ca2+.

Effects of anandamide on potassium channels in rat ventricular myocytes: a suppression of Ito and augmentation of KATP channels

2012 ◽  
Vol 302 (6) ◽  
pp. C924-C930 ◽  
Author(s):  
Qian Li ◽  
Hui-Jie Ma ◽  
Sheng-Li Song ◽  
Min Shi ◽  
Hui-Juan Ma ◽  
...  
Keyword(s):  
Steady State ◽  
Receptor Antagonist ◽  
Potassium Current ◽  
Ventricular Myocytes ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Concentration Dependent Manner ◽  
Inactivation Curve ◽  
Rat Ventricular Myocytes ◽  
Outward Potassium Current

Anandamide is an endocannabinoid that has antiarrhythmic effects through inhibition of L-type Ca2+ channels in cardiomyocytes. In this study, we investigated the electrophysiological effects of anandamide on K+ channels in rat ventricular myocytes. Whole cell patch-clamp technique was used to record K+ currents, including transient outward potassium current ( Ito), steady-state outward potassium current ( Iss), inward rectifier potassium current ( IK1), and ATP-sensitive potassium current ( IKATP) in isolated rat cardiac ventricular myocytes. Anandamide decreased Ito while increasing IKATP in a concentration-dependent manner but had no effect on Iss and IK1 in isolated ventricular myocytes. Furthermore, anandamide shifted steady-state inactivation curve of Ito to the left and shifted the recovery curve of Ito to the right. However, neither cannabinoid 1 (CB1) receptor antagonist AM251 nor CB2 receptor antagonist AM630 eliminated the inhibitory effect of anandamide on Ito. In addition, blockade of CB2 receptors, but not CB1 receptors, eliminated the augmentation effect of anandamide on IKATP. These data suggest that anandamide suppresses Ito through a non-CB1 and non-CB2 receptor-mediated pathway while augmenting IKATP through CB2 receptors in ventricular myocytes.

scholarly journals The influence of 8-prenylnaringenin on the activity of voltage-gated kv1.3 potassium channels in human jurkat t cells

2012 ◽  
Vol 17 (4) ◽  
Author(s):  
Justyna Gąsiorowska ◽  
Andrzej Teisseyre ◽  
Anna Uryga ◽  
Krystyna Michalak
Keyword(s):  
Potassium Channels ◽  
Cancer Cell ◽  
Inhibitory Effect ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Concentration Dependent Manner ◽  
Voltage Gated ◽  
Whole Cell Patch Clamp ◽  
Activation Rate ◽  
Kv1.3 Channels

AbstractUsing the whole-cell patch-clamp technique, we investigated the influence of 8-prenylnaringenin on the activity of the voltage-gated Kv1.3 potassium channels in the human leukemic T lymphocyte cell line Jurkat. 8-prenylnaringenin is a potent plant-derived phytoestrogen that has been found to inhibit cancer cell proliferation. The results show that it inhibited the Kv1.3 channels in a concentration-dependent manner. Complete inhibition occurred at concentrations higher than 10 μM. The inhibitory effect of 8-prenylnaringenin was reversible. It was accompanied by a significant acceleration of channel inactivation without any pronounced change in the activation rate. Of the naringenin derivatives tested to date, 8-prenylnaringenin is the most potent inhibitor of the Kv1.3 channels. The potency of the inhibition may be due to the presence of a prenyl group in the molecule of this flavonoid. The inhibition of the Kv1.3 channels might be involved in the antiproliferative and pro-apoptotic effects of 8-prenylnaringenin that have been observed in cancer cell lines expressing these channels.

Involvement of ceramide in inhibitory effect of IL-1 beta on L-type Ca2+ current in adult rat ventricular myocytes

1997 ◽  
Vol 272 (6) ◽  
pp. H2591-H2598 ◽  
Author(s):  
K. D. Schreur ◽  
S. Liu
Keyword(s):  
Ventricular Myocytes ◽  
Biological Effects ◽  
Inhibitory Effect ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Channel Current ◽  
Whole Cell Patch Clamp ◽  
Dependent Inhibition ◽  
Ceramide 1 ◽  
Ceramide Production

Interleukin (IL)-1 beta has previously been shown to decrease the L-type Ca2+ channel current (ICa,L). Because ceramide has been suggested to mediate many biological effects of IL-1 beta, we examined whether ceramide was involved in the IL-1 beta-induced suppression of ICa,L in adult rat ventricular myocytes. Exposure of myocytes to 5 ng/ml IL-1 beta elicited a 140% increase in ceramide production within 2 min, as measured with 32P phosphorylation. Whole cell patch-clamp techniques were used to measure ICa,L in myocytes internally dialyzed and externally perfused with Na(+)- and K(+)-free solutions. C2 ceramide (1 nM-1 microM), a membrane-permeable analog of ceramide, caused a concentration-dependent inhibition of ICa,L and increased the rate of ICa,L inactivation without altering its gating properties. An inactive ceramide analog failed to inhibit ICa,L. At submaximal concentrations, effects of C2 ceramide and IL-1 beta on ICa,L were additive and saturable. In the presence of a maximally effective concentration of IL-1 beta, C2 ceramide had no further effect on ICa,L. These results suggest that ceramide mediates IL-1 beta-induced suppression of cardiac ICa,L.

Effect of Intravenous Anesthetics on Inward Rectifier Potassium Current in Rat and Human Ventricular Myocytes 

1997 ◽  
Vol 87 (2) ◽  
pp. 327-334 ◽  
Author(s):  
Cynthia A. Carnes ◽  
William Muir ◽  
David R. Van Wagoner
Keyword(s):  
Potassium Current ◽  
Ventricular Myocytes ◽  
Plasma Concentrations ◽  
Dependent Manner ◽  
Patch Clamp Technique ◽  
Concentration Dependent Manner ◽  
Pipette Solution ◽  
Rat Ventricular Myocytes ◽  
Ventricular Cells ◽  
Drug Concentrations

Background Inhibition of the inward rectifying potassium current (I(K1)) may cause cardiac dysrhythmias by decreasing resting membrane potential or prolonging action potential. Methods The effects of thiopental, ketamine, and propofol on I(K1) conductance were evaluated in rat ventricular myocytes. The effect of thiopental on I(K1) conductance was also evaluated in human ventricular myocytes. Currents were recorded using the nystatin-perforated whole-cell patch-clamp technique (holding potential, -50 mV; test potentials, -140 to -40 mV). Pipette solution contained 130 mM KCl, 5 mM MgCl2, 5 mM HEPES, and 5 mM EGTA,pH 7.2. Bath solution (32 degrees C) contained 134 mM NaCI, 4 mM KCl, 1 mM MgCl2, 1 mM CaCl2, 0.3 mM CdCl2, 5 mM HEPES, and 5 mM d-glucose,pH 7.4. Drug concentrations examined encompassed the range of clinically relevant unbound plasma concentrations. Currents were normalized for cell capacitance. Conductance was calculated as current density/delta mV from -140 to -100 mV. Analysis of variance was used to test for changes in conductance as a function of drug concentration. Results Thiopental reduced I(K1) conductance in a concentration-dependent manner (P &lt; 0.0001). Thiopental-induced changes in I(K1) conductance in rat ventricular myocytes were fit to an inhibitory E(max) model, with a median inhibitory concentration of 10.5 microM. The effect of thiopental on I(K1) conductance in human ventricular cells was comparable to that observed in rat ventricular myocytes. Neither ketamine nor propofol altered I(K1) conductance. Conclusions Thiopental reduces I(K1) conductance in a concentration-dependent manner at clinically relevant concentrations in both rat and human ventricular myocytes.

1,2-Dioctanoyl-sn-glycerol depresses cardiac L-type Ca2+ current: independent of protein kinase C activation

1996 ◽  
Vol 270 (2) ◽  
pp. C655-C662 ◽  
Author(s):  
K. D. Schreur ◽  
S. Liu
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Ventricular Myocytes ◽  
Inhibitory Effect ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Kinase C ◽  
Whole Cell Patch Clamp ◽  
Steady State Inactivation ◽  
Slope Factor

The present study examines the effect of 1,2-dioctanoyl-sn-glycerol (DiC8), a diacylglycerol analogue, on L-type Ca2+ current (ICa,L) in adult rat ventricular myocytes using whole cell patch-clamp techniques. Extracellular application of DiC8 (1-10 microM) resulted in a concentration-dependent inhibition of peak ICa,L (half-maximum inhibitory concentration = 2.2 microM). Results obtained from the current-voltage relationship showed that DiC8 decreased the slope conductance. In addition, DiC8 increased the rate of Ba2+ current inactivation and caused a hyperpolarizing shift in the steady-state inactivation by 6 mV and a decrease in the slope factor. The DiC8-induced inhibition of ICa,L was neither mimicked by activation of protein kinase C (PKC) with 100 nM phorbol 12-myristate 13-acetate (PMA) no prevented by inhibition of PKC with 30 microM H-7, 100 nM staurosporine, or 24-h pretreatment with PMA. These results suggest that in rat ventricular myocytes 1) 1,2-sn-diacylglycerol (DAG) inhibits ICa,L, possibly by facilitating channel inactivation and decreasing channel availability and 2) this inhibitory effect of DAG is independent of PKC activation.

Effect of tetramethyl pyrazine on L-type calcium channel in rat ventricular myocytes

2001 ◽  
Vol 79 (7) ◽  
pp. 621-626 ◽  
Author(s):  
Lu-Yun Zou ◽  
Xue-Mei Hao ◽  
Guang-Qing Zhang ◽  
Mei Zhang ◽  
Ji-Hong Guo ◽  
...  
Keyword(s):  
Time Course ◽  
Ventricular Myocytes ◽  
Antagonistic Effect ◽  
Patch Clamp Technique ◽  
Inactivation Curve ◽  
Rat Ventricular Myocytes ◽  
Adult Rat ◽  
Whole Cell Patch Clamp ◽  
Steady State Inactivation ◽  
Ionic Mechanisms

To elucidate possible ionic mechanisms of antimyocardial ischemia and antiarrythmia of tetramethyl pyrazine (TP), we studied L-type Ca2+ currents (ICa.L) in adult rat ventricular myocytes using the whole-cell patch-clamp technique. The results showed: (i) under physiological conditions, 0.25 mmol/L TP decreased amplitude of ICa.L to 60.6% and this inhibition was increased with increasing concentration of TP. ID50 was 0.20 mmol/L. (ii) The Ca2+-antagonistic effect of TP was voltage-dependent. A marked negative shift of the steady-state inactivation curve was observed with long (10 s) conditioning prepulses, but not with short (350 ms) ones. (iii) The time course of inhibition during TP treatment was increased with an increase in drug concentration, and recovery from TP-induced inactivation of ICa.L was slower than in control cases. (iv) Tonic block and use-dependent block with TP treatment, which was induced by increasing the frequency of stimulation, occurred. We suggest that TP inhibits the ICa.L mainly by binding to inactivated Ca2+ channels. The high affinity of TP for the inactivated state of ICa.L may play an important role in developing therapies for pathological conditions.Key words: Tetramethyl pyrazine, L-type calcium current, rat ventricular myocytes.

Fluid pressure modulates L-type Ca2+ channel via enhancement of Ca2+-induced Ca2+ release in rat ventricular myocytes

2008 ◽  
Vol 294 (4) ◽  
pp. C966-C976 ◽  
Author(s):  
Sunwoo Lee ◽  
Joon-Chul Kim ◽  
Yuhua Li ◽  
Min-Jeong Son ◽  
Sun-Hee Woo
Keyword(s):  
Ventricular Myocytes ◽  
Fluid Pressure ◽  
Inhibitory Effect ◽  
Cellular Mechanism ◽  
Confocal Imaging ◽  
Rat Ventricular Myocytes ◽  
Whole Cell Patch Clamp ◽  
Current Voltage ◽  
Intracellular Ca ◽  
High Concentrations

This study examines whether fluid pressure (FP) modulates the L-type Ca2+ channel in cardiomyocytes and investigates the underlying cellular mechanism(s) involved. A flow of pressurized (∼16 dyn/cm2) fluid, identical to that bathing the myocytes, was applied onto single rat ventricular myocytes using a microperfusion method. The Ca2+ current ( ICa) and cytosolic Ca2+ signals were measured using a whole cell patch-clamp and confocal imaging, respectively. It was found that the FP reversibly suppressed ICa (by 25%) without altering the current-voltage relationships, and it accelerated the inactivation of ICa. The level of ICa suppression by FP depended on the level and duration of pressure. The Ba2+ current through the Ca2+ channel was only slightly decreased by the FP (5%), suggesting an indirect inhibition of the Ca2+ channel during FP stimulation. The cytosolic Ca2+ transients and the basal Ca2+ in field-stimulated ventricular myocytes were significantly increased by the FP. The effects of the FP on the ICa and on the Ca2+ transient were resistant to the stretch-activated channel inhibitors, GsMTx-4 and streptomycin. Dialysis of myocytes with high concentrations of BAPTA, the Ca2+ buffer, eliminated the FP-induced acceleration of ICa inactivation and reduced the inhibitory effect of the FP on ICa by ≈80%. Ryanodine and thapsigargin, abolishing sarcoplasmic reticulum Ca2+ release, eliminated the accelerating effect of FP on the ICa inactivation, and they reduced the inhibitory effect of FP on the ICa. These results suggest that the fluid pressure indirectly suppresses the Ca2+ channel by enhancing the Ca2+-induced intracellular Ca2+ release in rat ventricular myocytes.

Sign in / Sign up

Export Citation Format

Share Document